The present invention relates to a film dispenser for dispensing film such as that used in the packaging of food from a roll of such film.
Known film dispensers include a rotatable support around which a roll of sheet material is stored and a serrated elongated edge mounted at the mouth of a dispensing aperture. It is common with such dispensers to accidentally cut ones finger on the serrated edge during the film cutting or severing step. Another problem occurs once the severing step has been completed. Typically the serrated edge faces down from the top elongated edge of the mouth. Thus, in order to sever the film it is necessary to lift up and tear it from one side to the other. The latter action results in the film wrapping around on itself making it difficult to unwrap and straighten.
One method developed to overcome the latter problem is disclosed in Wallace J. Macgrory et al. U.S. Pat. No. 4,427,144 issued on Jan. 24, 1984 and assigned to EZY Wrap Products Pty. Limited of Australia. The Macgrory patent discloses the use of a heated wire to melt the film along a direction transverse to its direction of movement when being unravelled. The power applied to the wire heats it up until its reaches equilibrium with its surroundings and its temperature stabilizes. Usually the temperature of the wire is so high that it burns the film and causes the release of noxious fumes.
A solution to the overheating of the wire is disclosed in an earlier patent, namely H. Rosenthal U.S. Pat. No. 3,595,456 issued Jul. 27, 1971. The Rosenthal patent discloses the use of a heated wire in combination with a pivotal wire switch actuator which closes a normally open switch upon being forced to pivot upwardly by the film. The same actuator causes the switch to open after severance of the film by the heated wire is complete and shut off the current.
The above-mentioned Rosenthal patent also discloses a brake for restraining the film roll from unwinding during severance of the film. The brake consists of a manually operated solenoid that causes an elongated rod to engage a serrated disc affixed to the roller which supports the roll of film. The latter brake structure is complex and requires manual operation of a lever once the desired length of film has been withdrawn.
Most commercial endeavors to manufacture and market film dispensers have been unsuccessful due primarily to the inconvenience and lack of reliability of the products. Clearly, it is desirable to have a film dispenser with a minimum number of parts in order to minimize the cost and the likelihood of component failure. At the same time provision must be made for preventing the roll from unwinding once a desired length of film has been extracted. Also electrical heating of a wire should be used to avoid the injury that mechanical serrations can inflict and yet the heating must not produce noxious fumes while at the same time be able to sever a film of varying thickness without adjustment. Finally, the film end must be conveniently disposed after severance so that it may be grabbed and pulled out to a desired length.
Accordingly, a principal object of the invention is to provide an improved film dispenser that is simpler in construction and more reliable than previous film dispensers. A further object is to provide a film dispenser with a simple brake system that is easy to load.